PYPL - 2 years ago 93

Python Question

How do i filter all common sub dictionary keys that exists in other sub dictionary keys in the parent dictionary

`d = {`

'0': {'key_x': 0, 'key_y': 15, 'key_z': 41}

'1': {'key_x': 5, 'key_y': 22}

'2': {'key_x': 6, 'key_y': 41}

}

result ['key_x', 'key_y']

current solution is

`intersect = {}`

for k in corner_values.keys():

for j in corner_values[k]:

if j not in intersect:

intersect[j] = 1

else:

intersect[j] += 1

for k in intersect:

if intersect[k] != len(corner_values.keys()):

del intersect[k]

Is there any simpler solution for this?

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Answer Source

You can `map`

the dictionaries to `set`

and then `reduce`

using `set.intersection`

:

```
>>> from functools import reduce # if you are using Python 3
>>> d = {
... '0': {'key_x': 0, 'key_y': 15, 'key_z': 41},
... '1': {'key_x': 5, 'key_y': 22},
... '2': {'key_x': 6, 'key_y': 41}
... }
>>> reduce(set.intersection, map(set, d.values()))
{'key_x', 'key_y'}
```

Note: In Python 3, `reduce`

has been moved to `functools`

.

Update: As seen in @John's answer, `set.intersection`

can handle an arbitrary number of sets, so the `reduce`

is not even necessary. Just `set.intersection(*map(set, d.values()))`

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